Does python logging.handlers.RotatingFileHandler allow creation of a group writable log file?

Question

I\'m using the standard python (2.5.2) logging module, specifically the RotatingFileHandler, on a linux system. My application supports both a command-line interfa

Answer 1

I resorted to scanning the logging.handlers module and was unable to see any way to specify a different file permissions mode. So, I have a solution now based on extending the RotatingFileHandler as a custom handler. It was fairly painless, once I found some nice references to creating one. The code for the custom handler is below.

class GroupWriteRotatingFileHandler(handlers.RotatingFileHandler):

    def doRollover(self):
        """
        Override base class method to make the new log file group writable.
        """
        # Rotate the file first.
        handlers.RotatingFileHandler.doRollover(self)

        # Add group write to the current permissions.
        currMode = os.stat(self.baseFilename).st_mode
        os.chmod(self.baseFilename, currMode | stat.S_IWGRP)

I also discovered that to reference the custom handler from a logging config file, I had to bind my module to the logging namespace. Simple to do, but annoying.

from mynamespace.logging import custom_handlers
logging.custom_handlers = custom_handlers

References I found useful: binding custom handlers and creating custom handlers

Answer 2

Here is a simple solution worked fine:

import os

class GroupWriteRotatingFileHandler(handlers.RotatingFileHandler):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        os.chmod(self.baseFilename, 0o0777)  # You can change whatever permission you want here.

        # you can also change the group of the file:
        os.chown(self.baseFilename, uid, gid)   # pass the user_id and group_id you want to set 

Answer 3

Here's a complete solution for Django based on rob's solution. in my_module :

import logging
import logging.handlers
import os

The class= that happens during the logging configuration is evaluated in the namespace of the logging module, and by default this does not have a binding to handlers. So we have to put it in explicitly before we can extend it. See this SO article

logging.handlers = logging.handlers

It's this magical incantation that took me forever to find - I couldn't believe it did anything! Finally, Jon's class will load without errors.

class GroupWriteRotatingFileHandler(logging.handlers.RotatingFileHandler):    
    def _open(self):
        prevumask = os.umask(0o002)
        rtv = logging.handlers.RotatingFileHandler._open(self)
        os.umask(prevumask)
        return rtv

To use this for Django add the following this in the settings file

from my_module import GroupWriteRotatingFileHandler
logging.handlers.GroupWriteRotatingFileHandler = GroupWriteRotatingFileHandler

And then in LOGGING['handlers']['file'] you have

'class': 'logging.handlers.GroupWriteRotatingFileHandler'

Answer 4

It looks that def _open(self): worked with umask(0o000) to get all the permissions of -rw-rw-rw-.

os.chmod(self.baseFilename, 0o0777) failed with ValueError: Unable to configure handler 'some_handler': [Errno 1] Operation not permitted: if the log file has ownership of root:root that's different from running process's, such as testuser.

from logging import handlers

import logging
import os

class GroupWriteRotatingFileHandler(handlers.RotatingFileHandler):
    def _open(self):
        prevumask = os.umask(0o000)  # -rw-rw-rw-
        rtv = logging.handlers.RotatingFileHandler._open(self)
        os.umask(prevumask)
        return rtv

LOGGING = {
    'handlers': {
        'db_handler': {
                'level': 'DEBUG',
                'class': 'log.GroupWriteRotatingFileHandler',
                'filename': PATH_TO_LOGS + '/db.log',
                'maxBytes': maxBytes,
                'backupCount': backupCount,
                'formatter': 'standard',
        },

Log files:

logs]# ls -lrt
-rw-rw-rw- 1 root root 71 Apr  1 16:02 db.log

logs]# ls -lrt
total 0
-rw-rw-rw- 1 testuser testuser 0 Apr  1 16:20 db.log

Answer 5

$ chgrp loggroup logdir
$ chmod g+w logdir
$ chmod g+s logdir
$ usermod -a -G loggroup myuser
$ umask 0002

Answer 6

James Gardner has written a handler that only rotates files, not creating or deleting them: http://packages.python.org/logrotate/index.html